Apparatus for regulation of airflow to flame tubes for gas turbine engines

ABSTRACT

An annular flame tube for a gas turbine engine includes a primary combustion air inlet, a plurality of secondary combustion air inlets and a plurality of dilution air inlets, and variable flow restricting means associated with at least some of the said inlets so as to vary the ratio of secondary combustion air to dilution air, the inlets being formed as nozzles to provide deep penetration of secondary combustion air and dilution air into the flame.

United States Patent n91 Jackson et al.

l l 3,731,484 May 8,1973

[54] APPARATUS FOR REGULATION OF AIRFLOW TO FLAME TUBES FOR GAS TURBINE ENGINES [75] Inventors: Squire Ronald Jackson; Kenneth Greenwood, both of Burnley; Alban Heaton, Blackburn; Alwin Harrison, Burnley, all of England [73] Assignee: Joseph Lucas (Industries) Limited,

Birmingham, England 22 Filed: Oct. 29, 1970 [21] Appl. No.: 85,178

Related US. Application Data Division of Ser. No. 783,009, Dec. 11, 1968, Pat.

wafizzslat [52] US. Cl ..60/39.23, 60/39.65 [51] Int. Cl. ..F02c 3/06 [58] Field of Search ..60/39.23, 39.65; 431/165, 187, 351, 352

[56] References Cited UNITED STATES PATENTS Peterson ..60/39 23 UX 2,457,157 12/1948 King ..60/39.23 2,458,497 1/1949 Bailey t ..60/39.23 X 2,508,288 5/1950 Owner ..60/39.23 UX 2,621,477 12/1952 Powter ..60/39.23 2,655,787 10/1953 Brown ..60/39.23 2,715,816 8/1955 Thorn ..6()/39.23 UX 2,837,893 6/1958 Schirmer ..60/39.23 3,338,051 8/1967 Chamberlain 60/3965 Primary Examiner-Carlton R. Croyle Assistant ExaminerRobert E. Garrett Atl0rneyHolman & Stern [57] ABSTRACT An annular flame tube for a gas turbine engine includes a primary combustion air inlet, a plurality of secondary combustion air inlets and a plurality of dilution air inlets, and variable flow restricting means associated with at least some of the said inlets so as to vary the ratio of secondary combustion air to dilution air, the inlets being formed as nozzles to provide deep penetration of secondary combustion air and dilution air into the flame.

1 Claim, 7 Drawing lFigures Patented May-8,1973; 3,731,434

ATTOENEwg Patented -May 8, 1973 5 Shuts-Sheet MM! MMZVM 44M m mm INVENTOE' XTTOENEYS Patented May 8,1973 7 3,731,484

5 Shoots-sh 4 r 1 is:

IN VENTOE APPARATUS FOR REGULATION OF AIRFLOW TO FLAME TUBES GAS TURBINE ENGINES This invention relates to flame tubes for gas turbine engines, and is a divisional application from our U.S. Pat. No. 3,577,878 filed Dec. 11, 1968.

In the flame tubes of such engines, it is the practice for a minor amount of air, about 25-40 percent of the total air intake, to be employed for the combustion of fuel, the remainder being employed for cooling the flame tube, diluting of the flame and of the products of combustion before thelatter are allowed to enter the turbine stage of the engine. The air for combustion purposes is itself normally separated into primary and secondary streams entering along separate paths to the interior of the flame tube. In some engines which are required to operate over a wide range of fuel/air ratios, the combustion and dilution air quantities over some parts of the operating range are incorrect thus impairing combustion efficiency and giving rise to loss of performance over that part of the engine operating range.

The object of the invention is to provide a flame tube for a gas turbine engine in which this disadvantage is overcome or reduced.

In accordance with the invention there is provided an annular section flame tube for a gas turbine engine comprising an annular chaber having an annular primary combustion air inlet, at least one annular passage coaxial with the chamber, a plurality of secondary combustion air inlets opening into the chamber downstream of the primary combustion air inlet, a plurality of dilution air inlets opening into the chamber downstream of the secondary combustion air inlets, the said secondary combustion and dilution air inlets being formed as plunged holes directed inwardly of the chamber, whereby air flow through these inlets penetrates deeply into .the chamber, and air flow restricting means associated with the said secondary combustion and dilution air inlets and displaceable in one direction so as simultaneously to increase secondary combustion air flow and decrease dilution'air flow and displaceable in the other direction so as simultaneou sly toincrease dilution air flow and decrease secondary combustion air flow.

' Reference is now made to the accompanying drawings in whichz 1 FIG. 1 is a partial section through an annular flame tube incorporating one example of the present invennon,

FIG. 2 is a fragmentary front view of the arrangement shown in FIG. 1,

FIG. 3 is a section of another annular flame tube incorporating a further embodiment of the invention,

FIG. 4 is a section on line 4--4 in FIG. 3,

FIG. 5 is a section like FIG. 3 showing yet another embodiment of the invention,

FIG. 6 is a section on line 6-6 in FIG. 5, and

FIG. 7 is a sectional view illustrating a still further embodiment of the invention,

'The flame tube shown in FIGS. 1 and 2 has an annular combustion chamber 30 enclosed by a external tubular member 31 and an internal tubular member 32. The combustion chamber 31 has a series of primary air inlets 50 each provided with swirler vanes which are known per se. Secondary combustion air is introduced via inwardly directed nozzles 51, of which there are two in association with each of the primary air inlets. Dilution air is introduced at two stages in the flame tube, namely through a first series of nozzles 52 downstream of the nozzles 51 and through a second series of nozzles 53 downstream of the nozzles 52. The nozzles 53 are supplied via ducts 54 which open into intakes upstream of the nozzles 51. Nozzles 51, 52, 53 are in the form of inwardly directed plunged holes, whereby the seconda ry and dilution air flow therethrough penetrates deeply into the flame. The flame tube is provided with axially movable deflector vanes 55 which can be moved from the positions shown in FIG. 1 in which they cover the intakes to the ducts 54, to positions in which they cover intakes to the secondary combustion air nozzles 51. The ratio of dilution air to secondary combustion air may thus be varied, while the total air flow remains unaffected.

In the example shown in FIGS. 3 and 4 the flame tube has an axially slidable portion which telescopeswith a portion 101 formed with secondary air inlet nozzles 102. The portion 100 is formed with dilution air inlet nozzles 103. Nozzles 102, 103 are formed as plunged holes, similar to the nozzles of the embodiment of FIGS. 1 and 2. In the position shown in full lines in FIG. 3 the secondary air inlet nozzles 102 are fully open whereas the dilution air inlet nozzles 103 are restricted by a fixed wall 104. Movement of the portion 100 of the flame tube, however, causes partial closing of the secondary inlet nozzles 102 whilst the dilution air inlet nozzles 103 are fully opened.

Turning now to FIGS. 5 and 6 the flame tube in this case includes an outer rotatable wall and an inner rotatable wall 111. These rotatable walls carry a plurality of valve elements 112, 113 to co-act with secondary air inlet nozzles 114, 115 respectively and may additionally carry further valve members 116, 117 to co act with dilution air inlet nozzles 118, 119 respectively. The outer and inner rotatable walls 110 and 111 have ring gears 120, 121 respectively which engage pinions 123, 124 respectively on shafts linked by bevel gear trains to provide reverse rotation of the inner and outer walls on turning an input shaft 125.

In FIG. 7 the secondary air inlet nozzles and the dilution air inlet nozzles 131 are respectively controlled by valve members 132, 133 on opposite ends of a rockable lever 134 movable by apush rod 135 so that, in the positionshown in full lines the secondary air inlets are restricted, whereas in the position shown in dotted lines the dilution air inlet nozzles 131 are restricted.

Having thus described our invention which we claim as new and desire to secure by Letters Patent is:

1. An annular. section flame tube for a gas turbine engine comprising an annular chamber having an annular primary combustion air inlet, at least one annular passage coaxial with the chamber, a plurality of secondary combustion air inlets opening into the chamber downstream of the primary combustion air inlet, a plurality of dilution air inlets opening into the chamber downstream of the secondary combustion air inlets, a duct into which the secondary combustion air inlets open, a plurality of passages respectively connecting the dilution air inlets to said duct, said passages and. said secondary combustion air inlets being arranged in pairs, said secondary combustion and dilution air inlets being formed as plunged holes directed inwardly of the chamber, whereby air flow through these inlets penetrates deeply into the chamber, and a plurality of valve members in said duct movable in unison between positions in which they obstruct the secondary com- 5 bustion air inlets and positions in which they obstruct the entries to said passages. 

1. An annular section flame tube for a gas turbine engine comprising an annular chamber having an annular primary combustion air inlet, at least one annular passage coaxial with the chamber, a plurality of secondary combustion air inlets opening into the chamber downstream of the primary combustion air inlet, a plurality of dilution air inlets opening into the chamber downstream of the secondary combustion air inlets, a duct into which the secondary combustion air inlets open, a plurality of passages respectively connecting the dilution air inlets to said duct, said passages and said secondary combustion air inlets being arranged in pairs, said secondary combustion and dilution air inlets being formEd as plunged holes directed inwardly of the chamber, whereby air flow through these inlets penetrates deeply into the chamber, and a plurality of valve members in said duct movable in unison between positions in which they obstruct the secondary combustion air inlets and positions in which they obstruct the entries to said passages. 